RÉSUMÉ
We report an organocatalyst that combines a triazolium N-heterocyclic carbene (NHC) with a squaramide as a hydrogen-bonding donor (HBD), which can effectively catalyze the atroposelective ring-opening of biaryl lactams via a unique amide C-N bond cleavage mode. The free carbene species attacks the amide carbonyl, forming an axially chiral acyl-azolium intermediate. Various axially chiral biaryl amines can be accessed by this methodology with up to 99% ee and 99% yield. By using mercaptan as a catalyst turnover agent, the resulting thioester synthon can be transformed into several interesting atropisomers. Both control experiments and theoretical calculations reveal the crucial role of the hybrid NHC-HBD skeleton, which activates the amide via H-bonding and brings it spatially close to the carbene centre. This discovery illustrates the potential of the NHC-HBD chimera and demonstrates a complementary strategy for amide bond activation and manipulation.
RÉSUMÉ
A method for remote radical C-H alkynylation and amination of diverse aliphatic alcohols has been developed. The reaction features a copper nucleophile complex formed in situ as a photocatalyst, which reduces the silicon-tethered aliphatic iodide to an alkyl radical to initiate 1,n-hydrogen atom transfer. Unactivated secondary and tertiary C-H bonds at ß, γ, and δ positions can be functionalized in a predictable manner.
RÉSUMÉ
A catalytic asymmetric alkylation of azoles with secondary 1-arylalkyl bromides through direct C-H functionalization is reported. Under blue-light photoexcitation, a copper(I)/carbazole-based bisoxazoline (CbzBox) catalytic system exhibits good reactivity and high stereoselectivity, thus offering an efficient strategy for the construction of chiral alkyl azoles. These reactions proceed at low temperature and are compatible with a wide range of azoles.
RÉSUMÉ
An asymmetric copper-catalyzed Sonogashira type coupling between alkynes and α-bromoamides has been developed. This method represents a facile approach to synthetically useful ß, γ-alkynyl amides from two readily available starting materials in a highly enantioselective manner. A Bisoxazoline diphenylanaline (BOPA) serves as the effective chiral ligand. Preliminary mechanistic studies support the formation of alkyl radical species .
RÉSUMÉ
A rhodium-catalyzed tandem reaction of alkynyl cyclobutanols with salicylaldehydes has been developed. The reaction offers a new and atom-economical approach for the selective preparation of multisubstituted 2-(2-oxo-2-phenylethyl)cyclopentanone in high yields under mild reaction conditions with tolerance of a broad range of substituted alkynyl cyclobutanols and salicylaldehyes. The isolation of intermediate suggests that the reaction proceeds through a sequential process of intermolecular hydroacylation and semipinacol rearrangement.
RÉSUMÉ
A variety of 2-aminobenzonitriles were prepared from 2-arylindoles in good to excellent yields through tert-butylnitrite (TBN)-mediated nitrosation and sequential iron(III)-catalyzed C-C Bond cleavage in a one-pot fashion. The 2-aminobenzonitriles can be used to rapidly synthesize benzoxazinones by intramolecular condensation. The present method features an inexpensive iron(III) catalyst, gram scalable preparations, and novel C-C bond cleavage of indoles.
RÉSUMÉ
An efficient transition-metal-free method for the preparation of α,ß-unsaturated N-aryl ketonitrones under mild conditions has been developed. This reaction shows good functional group tolerance for both electron-rich and electron-deficient substituents on both oximes and diaryliodonium salts. Two examples of gram-scale preparations have been realized in good yields. Further transformations of these nitrones to different N-heterocycles have been demonstrated. DFT calculations suggest that N-arylation products are formed by [1,3]-phenyl migration of an O-coordinated oximate complex via a four-centered transition state, while the O-arylation products are formed by [1,3]-phenyl migration of a N-coordinated oximate complex.